Figure 5.

An inchworm translocation motor. The filament (green) is immobile and the dimer machine can actively translocate itself along it. (a) Initially, the left bead of the dimer is connected to the filament and holds it. (b) When a substrate arrives, a connection between the right bead and the filament is established and then the left bead gets disconnected. (c) The dimer contracts, bringing the left bead closer to the immobile right bead. (d) When a product is formed and instantaneously released, the left bead re-establishes a connection to the filament and becomes immobile, whereas the right bead is disconnected. (a*) The free dimer expands and reaches its initial conformation. After one cycle, its location on the filament is shifted by the distance Δl = l₀ − l₁. The inset shows an animal inchworm. See also the electronic supplementary material, video S2. (Online version in colour.)